Electric resistance seam welder



Jan. 21, 1964 Filed Feb. 14, 1962 J. J. RILEY ETAL ELECTRIC RESISTANCESEAM WELDER 2 Sheets-Sheet 1 Flc.

5;- IlIlIIUIIIIIIUlllllllllllllllllilllllILIIIIIIII'IIIIIIIU INVENTORJJOSEPH J. RILEY BY FOSTER R. wooDwARo Jan. 21, 1964 .1.J. RILEY ETAL3,119,005

ELECTRIC RESISTANCE SEM WELDER Filed Feb. 14, 1962 2 Sheets-Sheet 2INVENTORS JOSEPH J. RILEY BY FOSTER R. WOODWARD dltl ELECTRHC RESlSTANCESRAM lll/ELDER .lioseph Il. Riley and Foster 1R. Woodward, Warren,(Ehio, assignors to rlihe Taylor-Withheld Corporation, Warren, hio, acorporation or @hin Filed Feb. ld, 1962, Ser. No. 173,175 6 Claims. (Cl.2l9--82) This invention relates to seam Welders of the kind in which arotary electrode has its peripheral speed correlated with the workprimarily hy frictional interengagement between the electrode and workand has as its principal object the elimination of certain ohjectionaloperating characteristics of this relatively simple kind of machine. lnsuch apparatus the work may be moved relative to the axis or axes of oneor a pair of rotary electrodes hut a more common arrangement is to clampthe work (strip for example) in a fixed position and by means of acarriage move the electrode or electrodes into engagement with the work.Whatever the specific machine arrangement, the rotary electrode orelectrodes must accelerate to welding speed as the work is contacted andmust thereafter be driven at welding speed-all by the force developed bythe frictional interengagement with the work. Due to the substantialmass and inertia ot the electrodes and their mountings and considerablefriction inherent in the necessary rotary welding current transferdevices the peripheral driving forces commonly causo slippage betweenthe electrodes and work. This is objectionable for the followingreasons.

When welding thin workpieces the larger forces and greater slippageoccurring as the electrodes contact and move up onto the stock causesthe stock edges to buckle which not only mutillates the work but alsodelays the start of sound welding. When welding coated workpieces suchas tin plate or galvanized sheet or strip, for example, slippage greatlyincreases the pickup ot the coating material by the electrodes whichcontaininates the latter, decreases the quality of the weld or welds,and, of course, Jurther damages the work due to the appearance ofunprotected areas. lt is accordingly highly desirable to avoid slippagebetween the electrodes and work and this is accomplished in a novel andvery practical manner by the present invention.

ln seam welding machines where the rotary electrodes are positivelydriven ditliculty is encountered in synchronizing the peripheral speedof the welding wheels with the relative speed of the worl: and weldingthroat, particularly if the wheels are gear driven. lf knurledperipheral drivers are used the resulting knurled imprint is transferredto the work and may be detrimental, particularly when welding thin orcoated stock. ln the apparatus oi our invention, however, the peripheraledges of the wheels remain smooth and concentric and highqualitydelicate welding may be accomplished.

We accomplish the object of our invention by applying a kind ofhigh-slip or helper drive to the rotary electrodes which is set up toprovide a free-wheeling peripheral speed in the immediate range of thedesired welding speed. The power train used is of such character,however, that the electrodes may readily slow down or speed up to exactwelding speed by the inilnence of only slight frictional forces actingtangentially on the peripheries of the electrodes. These forces are muchsmaller than they would be if slippage occurred and are insuillcient tocause bulckling or removal of coatings. Any power or transmission meanshaving high-slip characteristics may be used. For example, we may employa rotary type of air motor which is preferred because of its simplicity,low cost, and ease of free-running speed regulation simply by varyingthe pressure of the air supnited States Patent O ice plied. Magneticclutches and various kinds of hydraulic couplings driven by electricmotors may also be used.

The above and other ohjects and advantages of the invention will becomeapparent upon consideration of the following speciiication andaccompanying drawing wherein there is disclosed a preferred embodimentof our invention.

ln the drawing:

FIGURE l is a side elevation of an electric resistance seam Welderconstructed in accordance with the principles of this invention;

FlGURE 2 is a fragmentary end view of the apparatus of FGURE l; and

FGURE 3 is a fragmentary sectional view taken along the line lll-Ill ofFIG URE l.

The illustrated seam Welder to which the invention is applied is of moreor less known construction having a hase lil mounting a track lll. onwhich is movably supported a C-irame ft2 by means o anti-frictionrollers i3. On the tree end of the lower leg or" the frame l is mounteda conductive carrier rotatably mounting a lower electrode wheel andhaving suitable means ld for adjusting its vertical position so that thetop of the electrode la will have proper engagement with the worn.Carrier .lll is connected through a flexible band 17 to a heavyconductor which leads to one or the secondary terminals ot the weldingtransiornier, not shown.

Slidably mounted for vertical movement in the free end ci the C-ramc l2is a second conductive carrier for mounting the upper electrode wheel2l. Carrier l@ is arranged to he moved upwardly and downwardly and tohave welding force transmitted through it hy a cylinder w :ich iscarried on top of the frame l2. Welding current is supplied to theelectrode 2l. through the carrier 19 and the lexible band 2.2 leading toa heavy fixed conductor Z3 which, in turn, is connected to the othersecondary terminal of the .veldinfy transtorrner. lt is well recognizedin the electric resistance seam welding art that the conduction of therequired heavy welding currents to the rotary electrodes presents aconsiderable problem and that many structural arrangements have beenproposed to erllciently conduct these currents to rotary mernherswithout excessive resistive heating and without excessive mechanicalfriction. In practice, one such arrangement is utilized in the rotaryjoints between the shafts of the wheels l, 2l and the carriers lil, il,but whatever the arrangement, considerable starting friction is inherentin the apparatus. This starting friction coupled with the substantialand inertia of the rotary electrodes and shafts has heretofore causedditlculty when welding thin stock, particularly.

To overcome the above problem and also to insure the subsequent smoothand non-slipping traverse or the welding wheels across the work, weprovide a high-slip drive for the electrode wheels l5, 2l by means ofthe following. Mounted on the shaft for the wheel lf3 and in drivingrelation therewith is the gear 25 which meshes with a driving pinion 2owhich, in turn, is driven through shaft 27 by a chain sprocket 2%. Asimilar drive is provided for the upper wheel 2l by means of gear 33,pinion 3a, shaft 3S and sprocket 3o. Sprocket 23 is driven through anendless chain 32 by a sprocket 3d which is driven by a gear air motor 3lcarried on the trame i2 by means of bracket El The air motor and thedrive linkage between the same and the wheel i5 are so selected thatsuicient power supplied to the wheel l5 to overcome mechanical frictionand when the wheel is in a free state to rotate the same at a peripheralspeed only slightly higher than the set welding speed of the seamWelder. ln the specific embodiment illustrated the overlapped workpieceste would be held in fixed clamps, not shown, and the welding speed wouldbe determined by the speed of rotation of the drive screw i2 which hasscrew-threaded connection with a member i3 projecting downwardly fromthe frame l2. f course, suitable means, not s iown, and preferablyhoused in the base l@ is provided to drive the screw i2 at variablerates of speed.

Upper electrode 2l is driven similarly to electrode l5 by means of anair motor 38 acting through sprocket 39 and a chain which is entrainedover sprocket 36. Air motor is carried by a spring biased swingingbracket 37 to permit oi substantial vertical movement of the upperelectrode 2l as will be understood.

When operating the apparatus described above, the electrodes il and maybe accelerated to their slightly excess welding speed by applying air tothe motors 3l and 33 while the electrodes are stili apart. After theycontact and welding orc is applied the welding current may be turned onand simultaneously the drive for screw d2 may be activated to begin thewelding traverse. The work 45 is, at this time, oi course, rigidly heldin suitable clamps and welding begins as soon as the electrodes contactand move up onto the work. By regulating trie air pressure supplied tothe motors 3l, the power applied to the electrodes i5, El may be broughtdown to only slightly above that required to maintain free rollingaction of the electrodes. This power is far below the potentialavailable from the tangential frictional forces acting through the radiiof the electrodes l5", 2i during welding traverse, and therefore theelectrodes l5, 2li instantly stall down to peripheral speeds synchronouswith the welding speed. As a result, the electrodes roll up onto thework in a smooth manner without any buckling or distortion ot the Workin the direction of weld and without any slippage between the electrodesand the work. Likewise, during the remainder of the welding traverse noslippage occurs between the work and the electrodes. The lack ofslippage greatly decreases the pickup of coating materials (tin, Zinc,lead, etc.) by the electrodes and, further, the electrodes are subjectto much less wear and deformation. Also, the arrangement greatly reducesstresses imparted to the work by the electrodes in the direction of weldso that there is a minimum or displacement of the molten and soitmaterial, resulting in a sounder and better appearing weld.

in accordance with known practice, air hammers 2d are mounted on thecarriers ld and i9 and have contoured tool ends to fit over theperipheral portions of the wheels t5, 2l, to maintain the same in sounduniform cross-sectional shape. The peening hammers 24 are preferablyoperated concurrently with the air motors 3i, 33 so that the electrodesmay be acted on and dressed over longer intervals of time than theintervals required for the actual welding. While the peening hammers 24operate to reduce the adverse eiiects of pickup and electrodedeformation, the overall eiciency is much further enhanced by thenon-slip characteristic of the present invention.

Since the electrodes i5, 2l may tend to rotate at a peripheral speedslightly faster than the welding s eed there is, oi course, always acomponent or force exerted by the electrodes toward the softened metaljust welded. Sometimes this causes buckling at the end of the weld. Toavoid this we have provided a limit switch 4S which is engaged by anactuator 44 adjustably mounted on the frame l2. Actuator lidi isadjusted to operate switch d5 as the electrodes l5, 2.5 closely approachthe end of the work, and through suitable obvious control means, notshown, the supply of air to the motors 3l, is cut oil by actuation ofswitch 45.

instead oi the actuator and switch i5 we may employ a synchronizingswitch as shown in U.S. Patent No. 2,634,353 to shut oil the air motorsas the end of weld is approached.

For our purpose, air motors are probably best suited to drive the rotaryelectrodes because of their low torque characteristic at high or freerunning speed and because they inherently have a high-slippagecharacteristic whereby they may be very quickly and easily slowed downfrom their free running speeds by the application of a slight additionalload. However, it is recognized that certain types of electric motors,hydraulic couplings, magnetic and friction clutches, etc. may beselected and/or tailored to impart our desired operating characteristic,and such alternate but equivalent methods are within the purview of ourinvention. Also, it should be obvious that the electrode or electrodesmay be driven directly from the high-slip drive or drives by frictionwheels engaging their per j ieries instead ot through the gearingutilized in the specific embodiment illustrated.

t should now be apparent that we have provided an improvement inelectric resistance seam welders which accomplishes the objectsinitially set out. Without adding appreciable apparatus or cost to thesimplest hind of such Welders (free Wheeling electrode or electrodes) wemay now weld very thin and delicate stock Without buckling or tearingand coated stock without stripping and with better consistent qualitybecause of improved electrode maintenance.

While we have illustrated our invention as applied to a double opposedwheel seam Welder where the wheels are carried by a movable frame itshould be readily understood that the principles of the invention areequally applicable to machines in which the work is moved as well as tomachines in which one of the electrodes is a conductive backup bar andonly one rotary electrode is used. Therefore, since various changes maybe made in the above speciiically described embodiment oi our inventionwithout departing from the principles of our invention reference shouldbe had to the appended claims in determining the scope thereof.

We claim:

l. ln an electric resistance seam Welder having a rotary weldingelectrode and means to effect relative movement or the electrode and thework to be welded at a desired welding speed, the improvement comprisinga low-torque higlbslip drive for said electrode to idle said electrodeat a peripheral speed approximately equal to said weldinfr speed, thearrangement being such that at the start of a welding cycle theelectrode may be iirst brought up to said approximate speed and while sorotating be brought into Contact with the work after which saidelectrode will be brought to exact welding speed by tie retardive orassistive action of frictional engagement between the electrode andwork.

2. Apparatus according to claim 1 further characterized in that saiddrive comprises a rotary type of air motor to which compressed air ofdifferent pressure may be supplied to vary the said peripheral speed ofthe electrode prior to engagement of the electrode with the work tothereby compensate for differences in welding speeds.

3. Apparatus accordinU to claim 1 further including a peening hammer forengaging and contouring the periphery of the electrode, and means torapidly actuate said hammer in a repetitive manner whereby thecircumtierential extent of the periphery or the electrode will be actedon during idling and welding rotation of thc electrode.

4. Apparatus according to claim l further including adjustable meansarranged to be actuated as the end of the line of weld is approached tode-energize said drive whereby said electrode leaves the Work underrotation caused solely by the irictional engagement between theelectrode and the work.

5. In an electric resistance seam Welder of the kind having a frame withtop and bottom members and means for mounting rotary electrodes on itstop and bottom members and arranged to have relative movement withrespect to workpieces to be Welded together by said electrodes theimprovement comprising a low-torque highslip drive for the lowerelectrode mounted on the lower member of the frame and operative to idlesaid lower electrode at a peripheral speed approximately equal to saidrelative speed between said workpieces and said electrodes, and asimilar drive for the upper rotary electrode mounted on the upper memberof said frame.

6. Apparatus according to claim 5 further characterized in that themeans mounting said upper electrode on said upper member includes meansfor moving said upper electrode toward and away from the lower electrodeand for applying welding pressure to said upper electrode, and saiddriving means for the upper electrode being References Cited in the leof this patent UNlTED STATES PATENTS 1,282,502 Wagner et al Oct. 22,1918 1,787,039 Gibb Dec. 30, 1930 2,023,085 Lavallee Deo. 3, 1932,957,975 Pearson Oct. 25, 1960 FOREIGN PATENTS 235,774 Germany June 20,1911

1. IN AN ELECTRIC RESISTANCE SEAM WELDER HAVING A ROTARY WELDINGELECTRODE AND MEANS TO EFFECT RELATIVE MOVEMENT OF THE ELECTRODE AND THEWORK TO BE WELDED AT A DESIRED WELDING SPEED, THE IMPROVEMENT COMPRISINGA LOW-TORQUE HIGH-SLIP DRIVE FOR SAID ELECTRODE TO IDLE SAID ELECTRODEAT A PERIPHERAL SPEED APPROXIMATELY EQUAL TO SAID WELDING SPEED, THEARRANGEMENT BEING SUCH THAT AT THE START OF A WELDING CYCLE THEELECTRODE MAY BE FIRST BROUGHT UP TO SAID APPROXIMATE SPEED AND WHILE SOROTATING BE BROUGHT INTO CONTACT WITH THE WORK AFTER WHICH SAIDELECTRODE WILL BE BROUGHT TO EXACT WELDING SPEED BY THE RETARDIVE ORASSISTIVE ACTION OF FRICTIONAL ENGAGEMENT BETWEEN THE ELECTRODE ANDWORK.